The process of chemical vapor deposition (CVD) is generally described as the use of chemical reactions to create free product species which condense to form a thin deposit film on a substrate. Several different methods for producing such chemical reactions are well known to those skilled in the art and are disclosed in such treatises as Microelectronic Materials by CRM Grovenor, Adam Hilger 1989 and Growth and Characterization of Semiconductors by Stradling et al, Adam Hilger 1990. These different CVD methods are used to grow several different species of composite and uniform materials such as III-V semiconductor heterostructures and diamond thin films.
For example, diamond synthesis at low pressures (1-100 Torr) by CVD using hydrocarbon gases has been a subject of great interest over the past two decades. The reason for this interest is that diamond films have a variety of commercial uses such as hard wear resistant coatings, heat sinks which require high thermal conductivity, low dielectric constant coatings for multi-chip modules, as well as having applications in solar blind UV detectors and other high temperature devices such as diodes and transistors. An example of an outline description of diamond synthesis using CVD is found in, "Low Pressure, Metastable Growth of Diamond and `Diamondlike` Phases," by Angus and Hayman in Science, August, 1988, pages 913-921. Since the inception of this technique, a number of chemical vapor deposition techniques have been proposed to grow polycrystalline diamond films; these include: hot filament CVD (HFCVD) (see, U.S. Pat. No. 5,186,973, issued to Garg et al on Feb. 16, 1993), RF plasma assisted CVD, microwave plasma assisted CVD (See Japanese Patent No. SHO 63(1988)-307196 by Kokai, published Dec. 14, 1988), DC plasma assisted CVD (see, "High-Rate Synthesis of Diamond Film by DC Plasma Jet CVD," Koshino et al, Extended Book of Abstracts, MRS Conference on Diamond and Diamond-like Materials Synthesis, April 1988), laser assisted CVD, and microwave enhanced CVD (see, U.S. Pat. No. 5,015,494, issued to Yamazaki on May 14, 1991).
For example, microwave enhanced CVD utilizes microwaves to energize a reactive gas into a plasma state by virtue of a magnetic field which functions to contain the plasma gas within the excitation space. With this method, the substrate is held stationary and located at a distance from the excitation space to prevent sputtering. Once the reactive gas is in a plasma state, the plasma is extracted via a divergent magnetic field from the excitation space to a deposition space where the substrate is located. However, because the substrate is held stationary, the type and condition of the substrate directly effects the properties of the diamond film.
Accordingly, because the interface of the substrate and thin film are generally less than what is desirable, these methods have not produced diamond films that are suitable for incorporation into commercial electronic devices. The main problem with these methods is that they do not consistently produce uniform films with the required electrical properties or these methods produce films that are simply too fragile to use in any application.
Similarly, growth of semiconductor heterostructures using CVD has been limited to systems which can only operate in a continuous mode or only in a pulsed mode. Thus, those skilled in the art would readily appreciate a CVD system which can produce reliable commercial grade diamond thin films as well as produce semiconductor heterostructures or thin films in a continuous or pulsed mode. The present invention addresses these needs.